gistfile1.j

- (void) setScale: (CPString) scale origin: (CPString) origin
{
    var fScale = parseFloat(scale);
    // commenting out this log makes it stop working
    CPLog("asdf");

    // The slider updates fine 
    [_zoomSlider setDoubleValue:fScale * 100.0];

    // This sets up a CGAffineTransform, it only works if the CPLog is present
    [_cropView._imageLayer setScale: fScale];

    // this has no effect
    //[[CPRunLoop currentRunLoop] performSelectors];

}

Never mind, I was stupid. The image hadn't actually loaded yet, CPLog was introducing the necessary delay.